I have a pair of Sennheiser HD 590 headphones, which I really like. However, because they're open-air, I can't use them to listen to music in bed late at night when my wife is trying to sleep, because the music is quite audible to her at normal listening levels. For the same reason, I can't use them as studio monitors while I'm recording, because the sound bleeds through. So I'm looking for a pair of sound-isolating (not noise-canceling) headphones in the $100-150 range. For many years in the 1970s and 1980s, I owned a pair of Koss Pro-4AA headphones, and they sounded great. They were heavy and could get uncomfortable after extended wear, but I got used to them, for the most part. I'm considering getting another pair, but I wanted to see if anyone here has other suggestions. A few years ago, I read that iPods had trouble driving the Pro-4AAs at reasonable volume levels. I don't know know whether that was true, or, if so, whether it applies to today's iPhones and iPads. I listen to pop, rock, folk, jazz, classical, and a variety of other styles, and I like a flat response.